1. Field of the Invention
The present invention relates to a bag-making method, more specifically, the present invention relates to a bag-making method of producing a bag by melt-bonding a mouth member formed of a synthetic resin and a bag unit formed of a flexible film to ensure excellent liquid tightness at the melt-bonded part between the mouth member and the bag unit. Furthermore, the present invention relates to a medical container used after filling a transfusion solution or blood in the container produced by the above-described bag-making method.
Priority is claimed on Japanese Patent Application No. 2002-314252, filed Oct. 29, 2002.
2. Description of Related Art
In recent years, a medical container formed by using a synthetic resin is often used in place of a glass-made medical container. The synthetic resin-made medical container includes a container produced by blow molding and a container produced from a film or a sheet (hereinafter, a film and a sheet are collectively called a “film”) obtained by inflation molding or T-die casting. Among these, a container produced from a film (hereinafter referred to as a “film bag”) is increasing, because the film bag is thin and uniform in the container thickness and can be reduced in the volume after use, the waste is therefore less generated and at the transfusion, the discharging rate of liquid content can be kept almost constant until the last. In the film bag, a mouth member which is a hollow cylindrical body formed of a synthetic resin and having a three-dimensional shape as shown in FIG. 1 is fixed by heat sealing so as to enable filling or discharging of the content. The mouth member has a hollow circular or elliptic cross-section in many cases.
In the fixing of the mouth member to the film, a three-dimensionally shaped member must be fixed to a two-dimensional planar film and as shown in FIG. 2, a gap 22 is sometimes generated between the A-frame part of the film and the melt-bonding part of the mouth member (hereinafter referred to as a “A-frame part gap”) to cause leakage of the liquid content. Particularly, in the case of a thick film having a film thickness of 100 μm or more, the film is deformed in agreement with the shape of the mouth member at the heat sealing, though this may vary depending on the shape of the mouth member, and the once sealed portion is sometimes separated due to restoring stress of the film. Furthermore, on melt-bonding the mouth member and the film by sandwiching these with a sealing mold, the film is subject to an excess tensile stress so as to agree with the shape of the mouth member and this bears a risk of thinning the film or forming a hole in the film.
For preventing such deformation or hole formation of film, a method of stacking a heat-resistant layer on the film by using an adhesive to obtain a laminate film enhanced in the heat resistance is known. However, use of an adhesive is not preferred in the medical field because the adhesive sometimes dissolves out. Accordingly, various studies have been made for the bonding technique of causing no dissolving out of a material and enabling liquid-tight bonding without generation of a gap between a mouth member and a bag unit comprising a single-layer or multilayer film.
As the container succeeded in solving the problem of the A-frame part gap, a container obtained by bonding a bag unit and a mouth member provided with, as shown in FIG. 3, a thin strip 23 outwardly extending in the left and right sides of the melt-bonding part has been proposed.
Specific examples of the method for producing a container by bonding a container body and a mouth member provided with a thin strip outwardly extending in the left and right sides of the melt-bonding part include: a method of producing a mouth member having previously provided thereon thin strips by using a preheating jig and then heat-sealing it to a transfusion bag (see, Patent Document 1);
a method of melting the surface of an opening plug at a temperature higher by 15 to 80° C. than the melting point of the material for the opening plug before the opening plug comes into contact with a film or a sheet, simultaneously forming a fuse-bonding tab in the width of 0.2 to 3 mm on both sides of the opening plug, and pressing two sheets of film or sheet to the opening plug from the symmetrical directions to fuse-bond the films or sheets to the opening plug (see, Patent Document 2);
a method of providing a protruding part on the outer circumferential face of a hollow cylindrical body at symmetrical positions dividing the hollow cylindrical body into two in the perpendicular axial direction, with the joining part to the hollow cylindrical body being narrowed, heating and softening the protruding parts and then abutting a sheet to the protruding parts and hollow cylindrical body in the softened state (see, Patent Document 3);
a method of heat-sealing an inflation tube to a mouth part having fin-like protrusions formed by a metal mold and thereby producing a bag (see, Patent Document 4); and
a method of, before melt-bonding an opening plug to a film or a sheet, heating the surface layer at the melt-bonding part of the opening plug in the temperature range from the softening temperature of the material for the melt-bonding part of the opening plug to a temperature 13° C. higher than the melting point by utilizing radiation heat of a heater at a temperature of 600 to 800° C., pressing the heated opening plug from both sides by fin-forming metal molds symmetrical with respect to the opening plug to form fin-like thin strips on the opening plug, inserting the opening plug still in the heated state between films or sheets, and melt-bonding the opening plug to the films or sheets by a heat-sealing mold (see, Patent Document 5).
These are a method of producing a mouth member having previously provided thereon a thin strip outwardly extending in the left and right sides of the mouth member at the part to be melt-bonded to a film, and then bonding the mouth member to a bag unit. Such a method not only requires an excess step for forming a thin strip but also encounters problems at the formation of the thin strip, such as fluctuation in the size of thin strip, unevenness in the size between left and right thin strips and attachment of carbide debris from the thin strip-forming mold. In addition, the previously formed thin strip may be deformed, for example, may be shrunk, distorted or fallen down. Furthermore, the heating is readily accompanied with deformation of the mouth member due to release of a residual stress in the melt-bonding part generated at the injection molding of the mouth member, as a result, the positions of the mouth member, bag unit and sealing mold cannot be exactly adjusted at the bonding of the mouth member to the bag unit, resulting in unsatisfactory bonding. Accordingly, improvements for more completely preventing the generation of a A-frame part gap are being demanded.
Particularly, in the case of a large size mouth member with a diameter exceeding 10 mm, thinning of film and generation of pinhole are liable to more often occur.
Patent Document 1
JP-UM-A-61-194638 (the term “JP-UM-A” as used herein means an “unexamined Japanese published utility model application”)
Patent Document 2
Japanese Patent No. 2,940,987
Patent Document 3
Japanese Patent No. 2,791,387
Patent Document 4
JP-A-4-191033 (the term “JP-A” as used herein means an “unexamined Japanese patent application”)
Patent Document 5
Japanese Patent No. 3,048,486
Patent Document 6
JP-B-3-5304 (the term “JP-B” as used herein means an “examined Japanese patent publication”)